The migration and release of heavy metals during thermal treatment of municipal solid waste (MSW) is an environmental issue of great concern. Chlorine-containing compounds present in MSW could convert heavy metals into smaller particles and volatile chlorides during thermal treatment, thus cause serious environmental pollution. In this study, thermogravimetric analysis and tube furnace were used to investigate the effect of polyvinyl chloride (PVC) on the transformation and migration of Pb under different atmosphere. The results showed that PVC decomposed at 250℃, and then the released HCl reacted with PbO to form PbCl2 (melting point: 501℃), which promoted the migration of Pb into the flue gas. The concentration of PVC (at the molar ratios of Cl:Pb = 2, 3, 5, and 10) had no significant effect on the volatilization of Pb under air atmosphere. While under N2 atmosphere, the highest volatility of Pb could reach 88.19% at the molar ratio of Cl:Pb=3; the lowest volatility of Pb was 68.60% at the molar ratio of Cl:Pb=2.